The present invention relates generally to deployable antenna reflectors, and more specifically, to deployable reflectors having foldable elements that bend into space conserving positions. A reflecting structure according to the invention has at least one foldable, bendable element that has memory as to shape, such that when deployed, the foldable element adopts a predetermined, reflective shape.
In most, if not all, space vehicles, some form of deployable antenna reflector is required. Most are required to be stowed in as compact a disposition as possible in order to save space on board the spacecraft for other components. In general, the antenna reflectors in a deployed state take up substantially more volume than in their stowed state. Various structures have been used in the past to accomplish the dual-states of being stowed and deployed, but each is believed to have one or more limiting features, either from a structural or performance standpoint, or from a cost and manufacturability one.
Examples of known reflectors include that which is described in U.S. Pat. No. 4,989,015 to Chang, wherein a deployable antenna has a rigid central truss which carries circumferentially spaced booms. The booms support a flexible mesh reflecting surface service, which in the deployed state, adopts a concave, paraboloid shape. The mesh may be connected to the front of a cable supporting structure by tying, bonding or other mechanical connectors.
Further examples include U.S. Pat. No. 5,104,211 to Schumacher et al., in which a deployable solar panel has a plurality of radially disposed ribs and interconnected truss structures supported from a central hub. The ribs support a semi-rigid reflective surface structure consisting of a plurality of thin, flat reflective panel strips. Overall, the ribs resemble the supporting structure of an umbrella. The reflective strips are made of a low mass graphite-epoxy over which a reflective coating, such as vapor deposited silver is formed.
Yet another example of prior deployable structures is seen U.S. Pat. No. 5,421,376 to Sinha, wherein a deployable parabolic reflector has a metalized mesh fabric reflecting surface. The reflectors can be used in mobile and portable ground stations. The reflector is deployed in a parabolic shape, and includes a plurality of panels supported on ribs.
Another wire mesh deployable antenna reflector is shown in U.S. Pat. No. 5,864,324, issued to Acker et al., wherein a mesh reflector is made of a woven mesh material supported on radially extending ribs. The ribs are telescopic so that the deployed antenna reflector is substantially larger in volume than when stowed.
U.S. Pat. No. 5,255,006 to Pappas et al. describes a collapsible satellite, apparatus, in which rigid panels are connected to a base. When the rigid panels are rotated outwardly from a stowed position, the apparatus adopts a parabolic shape suitable for use as an antenna reflector. A similar parabolic reflector is disclosed in U.S. Pat. No. 5,257,034 to Turner et al.
U.S. Pat. No. 5,446,474 to Wade at al. discloses a re-deployable and furlable rib reflector which is movable between stowed and deployed positions. The reflector includes a central hub to which are connected a plurality of ribs. A ring assembly brings the rib furling elements into contact with the ribs for furling or unfurling about the hub.
In various known devices described above, the mechanisms used for furling and unfurling the reflecting structures relatively complex; in general, the more mechanical parts, the more prone the apparatus will be to failure in terms of binding during deployment. Also, mesh reflectors, although effective, are expensive to produce due to the complexity of conforming the mesh to a parabolic or other concave shape. Thus, a continuing need exists for deployable reflective structures that are relatively simple in construction, with a minimum of moving, mechanical parts.
An object of the present invention is to provide a deployable reflector which has a minimal number of moving parts for moving deployable elements from a stowed position to a deployed position.
Another object of the present invention is to provide a deployable reflector that is relatively simple in construction and cost effective to produce.
Still another object of the present invention is to provide a reflector that is light weight, thermally stable, and stowable in a substantially smaller volume than its deployed volume.
These and other objects are met by providing a deployable reflector apparatus which includes at least one rigid section having a reflective surface and at least one bendable section having a reflective surface and being connected to the rigid section, the bendable section further being movable between a first, stowed position in which the reflective surface of the bendable section is at least partially overlapping with the reflective surface of the rigid section, and a second, deployed position in which the reflective surfaces are continuous and non-overlapping.
Preferably, the apparatus includes a single, continuous piece of reflective material having at least one section connected to, and thereby rigidized by, a stiffening member. The reflective material is bendable and provided with shape memory, such that when bent away from its original form, it naturally springs back to its original form when the bending forces are released. The bending forces never exceed the yield strength of the material.